In its back-and-forth legal wrangling with the FBI over a killer's locked iPhone, Apple got a final word in Tuesday — arguing again in court papers that forcing the company to help federal officials access the phone would be illegal and dangerous.

The filing in U.S. District Court in Riverside was the latest turn in a heated and high-stakes struggle over the encrypted iPhone used by Syed Rizwan Farook, one of two assailants who attacked the Inland Regional Center in San Bernardino on Dec. 2, killing 14 and leaving many more wounded.

Officials have concluded that the killings by Farook and his wife, Tashfeen Malik, were an act of terrorism.

The case has become a battleground in a broader dispute among elected officials, law enforcement and technology executives over how far companies must go in aiding criminal investigations.

With several briefs from both sides filed and a hearing in front of U.S. Magistrate Judge Sheri Pym scheduled for next week, attorneys for Apple took one more swipe at the case U.S. Atty. Eileen Decker's office has made.

At the crux of the fight has been the All Writs Act, a sweeping, centuries-old law intended to provide judges the authority to issue orders when other avenues are unavailable. Prosecutors have insisted the act provides a solid legal foundation for Pym's order that Apple write new software to allow FBI agents to circumvent security features built into the iPhone Farook had used.

In its latest filing, Apple repeated its assertion that applying the act in this case would be wrong since it does not permit judges to make rulings that go beyond the limits of existing law. Congress, Apple wrote, has considered passing legislation that would force companies to develop software at the government's behest, but rejected the idea.

The company also reiterated the argument that being forced to write computer code would violate its constitutional rights, since courts have found that written code is akin to speech.

After the attack that ended with Farook and his wife dying in a shootout with police, a judge issued a warrant to allow the FBI to search the phone's contents. After lengthy discussions, Apple refused the agency's request for help.

Pym last month issued the order compelling Apple's assistance, but gave the company time to make its case.

Attorneys for the company continued Tuesday to portray the government's demand as being the cusp of a slippery slope. The requested computer code, they have argued, would amount to a master key that hackers could use to access any iPhone.

Prosecutors have rebuffed the idea, saying Apple would retain control of the code.

A version of this article appeared in print on March 16, 2016, in the News section of the Los Angeles Times with the headline "Apple stands by its legal claim - The company reasserts in court papers that forcing it to help the FBI unlock a terrorist's iPhone would be wrong." —
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